rttwtf  of  ihe  Uniied  Stales  Governmiii. 

i  No    20,  Revised  Edition 

United  States  Departmenl  of  Agrj 

// 

t  / 

libranr* 


BUREAU  OK   ENTOMOLOGY, 
i    '■   HOWARD.  Km. >ni.>i. mint  and  ChM    'it 


mi:   wooi.n    \niis  OF  Tin: 

m ■ 1 

i  ]<chizonauru  lanigera  Elausmann.) 


I..   M  M.I  \  i  i , 

.;;./       Iv.l  ^lillll    I    llli  I    ill     I 


.[.    vrri:  \i;  \\.  i:    wi>  uktiioh  ok  work. 

Throughout  tli<-  -uiniiirr  on  the  lower  portion  <»f  the  trunk  and  par- 
ticularly <>n  the  water  sprouts  of  the  apple  may  often  be  Been  small 
bluish-white  Hocculent  i>r  cottony  patches,  which  indicate  the  presence 
of  oolonies  of  our  of  the  worst  enemies  of  tin'  apple,  viz,  the  insecl  vari- 
ously known  in 
this  country  as  the 
"  apple-root  plant- 
. "  "woolly 
apple     louse," 

"  woolly    ,i  ph  i-." 

etc.,  ami  abroad 
very  generally  as 
the  "American 
blight."    It  i 

in   two  forms,  the 

one   ju.-t    referred 

to,  above  ground 

on    the    trunk    or 

Wat)  r  shoots,  and  &  o 

anotherinhabiting  , ..   ,    u  ,,  .   ,pb     M  ■  ,,  lnr_ 

tin1   r>  m  >t  9  am  In.''  < 

'i.ni  rpm.n  '       nal.) 

open  to  observa- 
tion.    Clow  !y  paralleling  in  these  particulars  the  grape  phylloxera,  the 

damage  from  the  woolly  aphis  i-  also  almost  altogether  'lu>'  to  the  root 
form,  tin'  atrial  colonies  causing  Bcarcely  any  injury.  On  the  roots 
attacks  induce  enlargements  <>r  ^nlls  or  Bwellings  very  similar  to  those 
produced  by  the  phylloxera,  ami  in  the  cracks  of  these  galls  and  BWell- 
the  root  form  occurs  in  clustered  masses.  The  injury  to  the  trees 
is  tlue  both  to  the  Bucking  up  ami  exhaustion  of  the  vital  plant  juices 
ami  to  the  poisoning  of  the  parts  attacked,  as  indicated  by  the  ( 
quent  abnormal  growths. 

The  damage  i-  particularly  serious  in  the  case  of  ni  tock  ami 

young  ire--  and  i-  less  often  important  after  the  tree  lias  once  become 
well  established  and  of  Bom<    -  Where  this  insect  i~  abundant  all 


the  roots  of  a  young  tree  to  the  depth  of  a  foot  or  so  hecome  clubbed 
and  knotted  by  the  growth  of  hard  fibrous  enlargements,  with  the  result, 
in  a  year  or  two,  of  the  dying  of  the  rootlets  and  their  ultimate  decom- 
position with  attendant  disappearance  of  the  galls  and  also  of  the  aphides, 
so  that  after  this  stage  is  reached,  the  cause  of  the  injury  is  often 
obscure.  On  the  trunks  the  presence  of  the  aphides  sometimes  results  in 
the  roughening  of  the  bark  or  a  granulated  condition  which  is  particularly 
noticeable  about  the  collar  and  at  the  forks  of  branches  or  on  the  fresh 
growth  around  the  scars  caused  by  pruning,  which  latter  is  a  favorite 
location.  On  the  water  shoots  the  insects  collect  particularly  in  the  axils 
of  the  leaves,  often  eventually  causing  them  to  fall,  and  on  the  tender 
greener  side  of  the  stems.  The  damage  above  ground,  though  com- 
monly insignificant,  is  useful  as  an  indication  of  the  probable  existence 
of  the  aphides  on  the  roots.  A  badly  attacked  tree  assumes  a  sickly  ap- 
pearance and  does  not  make  satisfactory  growth  and  the  leaves  become 
dull  and  yellowish,  and  even  if  not  killed  outright  it  is  so  weakened  that 
it  becomes  especially  subject  to  the  attacks  of  borers  and  other  insect 
enemies.  Injuries  from  the  woolly  aphis  are  almost  altogether  confined 
to  the  apple,  even  the  wild  crab  not  being  so  liable  to  attack  or  at  least 
injur}'  by  it.  There  is,  however,  some  difference  exhibited  by  different 
varieties  of  apple  in  immunity,  and  particularly  is  the  Northern  Spy 
proof  against  it,  and  it  is  possible  that,  as  in  the  case  of  the  grape 
phylloxera,  by  employing  root  stock  from  seedlings  of  the  more  resist- 
ant varieties  or  from  wild  crabs,  considerable  protection  would  result. 
The  character  of  the  soil  also  exerts  some  influence — that  is,  loose  dry 
soils  are  favorable  and  wet  compact  ones  are  unfavorable  to  the  aphis. 

ORHilX   AND   DISTRIBUTION. 

There  is  considerable  difference  of  opinion  as  to  the  origin  of  the 
woolly  aphis  of  the  apple.  The  belief  has  fluctuated  between  a  Euro- 
pean and  an  American  origin  for  this  insect,  but  the  weight  of  evidence 
seems  to  indicate  the  latter.  At  any  rate,  it  is  an  insect  which  is  most 
readily  carried  from  place  to  place  with  nurserj-  stock  of  the  apple,  and 
it  has  been  so  transported  to  practically  all  the  important  countries  of 
the  world  which  have  been  reached  by  colonization  or  European  settle- 
ment. The  woolly  aphis  was  first  noticed  in  England  in  17S7,  on  some 
stock  imported  that  year  from  America,  and  was  early  called  the  Ameri- 
can blight.  Hausmann  described  it  in  1801  as  infesting  apple  trees  in 
Germany,  and  within  the  next  twenty-five  years  it  was  recognized  as  a 
serious  enemy  of  this  fruit  tree  throughout  England,  Belgium,  northern 
Erance,  and  Germany,  but  seems  never  to  have  been  especialhy  notable 
in  the  warmer  latitudes  of  Europe. 

It  was  very  early  introduced  into  Australia  and  New  Zealand,  and  is 
known  in  India  and  Chile,  and  probably  is  as  widespread  as  any  of  the 
common  injurious  fruit  pests.  Notwithstanding  the  possibility  of  its 
being   a  native  American   insect,  it  did   not   attract  attention  in  this 


country  much  before  I860.  It-  Bpread  wnce  has,  however,  been  rapid, 
and  ii  now  occur-  practical lj  wherever  the  apple  is  grown,  It  has 
been  reported  to  this  Bureau  from  no  less  than  thirty-fiv<  3l  ttee  and 
Territoriee  and  nearbj  one  hundred  localities.  It  i-  particularly  abun- 
danl  and  injurious  in  the  latitude  of  the  Ohio  Valley.  While  seem 
ingly,  therefore,  somewhal  affected  bj  Bevere  cold,  it  is  able  to  thrive 
in  the  climate  of  the  northern  tier  ol  States  on  the  one  band  and  in 
thai  of  Louisiana,  New  Mexico,  and 
southern  Californii the  other. 

n  k  ii  R  \l.   lll-ToKY    and    BABTTS. 

In  common  with  most  aphides, 
this  species  lias  a  complicated  life 
history .  some  of  the  details  of  which 
arestill  lacking.  Thecommon  tonus, 
both  on  the  roots  and  above  ground, 
wingless  aphides,  not  exceeding 
one-tenth  of  an  inch  in  length,  and 
of  a  reddish-brown  color,  and  abun- 
dantly covered,  especially  in  the 
aerial   form,  with  a   Bocculenl  waxy 

retion.      These     arc     so-called 

agamic  females  and  reproduce  them- 
selves by  giving  birth,  as  obsei 
by  many  entomologists,  to  living 
young  indefinitely,  perhaps  tor  years, 
without  the  intervention  of  other 
forms.  The  newly  horn  larva-  have 
none  of  the  white  excretion,  which, 
however,  soon  appear-  as  a  minute 
down     when     they     begin     to     feed. 

These  aphides  are  also  peculiar  in 
lacking  the  honey  tubes  common  to 
most  aphides,  bul  exude  the  honey- 
dew  from  the  tip  of  the  body.  In  '  October  or  November,  or  earlier  in 
South,  among  the  wingless  ones  numbers  of  winged  individuals 
appear,  which  are  also  all  females,  and  are  the  parents,  as  shown  by 
the  observations,  partly  unpublished,  of  M<  bstb.  Howard  and  Pergande, 
oi  a  true  Bexed  generation  of  minute,  wingless,  larviform  aphides,  the 
females  of  which,  as  in  the  case  of  the  -rape  root-aphis,  give  birth  to  a 
single  "winter  egg."  This  egg  is  attached  within  a  crevice  of  the 
hark,  and,  probably,  following  the  analogy  of  the  phylloxera,  hatches 
in  the  spring  into  a  female  aphis  which  originates  a  new  aerial  colony. 
The  winged  females  appear  somewhat  abundantly  in  autumn,  and  are 
one  of  the  means  of  the  dispersal  ol  the  inseel       They  arc  very  minute. 


I  w 

a,  Rool  ■>:  \  iui  (rating  deforma- 

tion 

. 

i 


clear-winged,  gnat-like  objects,  greenish-brown,  almost  black  in  color, 
with  the  body  covered  with  more  or  less  of  the  cottony  excretion. 

The  aerial  colonies  are  probabh-  killed  out  every  winter  in  the  colder 
northern  districts,  but  in  the  warmer  latitudes  the  partly  grown  indi- 
viduals, at  least,  survive  protected  in  crevices  or  under  bits  of  bark, 
and  remain  more  or  less  active  during  winter  and  renew  the  colonies 
the  following  spring.  This  has  been  shown  to  be  true  in  the  District 
of  Columbia,  and  also  in  the  interior  regions  of  the  same  latitude,  in 
spite  of  the  much  colder  winters.  The  root  form  survives  the  winter 
usually  in  an  immature  condition,  viz,  larvae  in  various  stages  of 
development,  and  both  in  latitudes  where  the  aerial  forms  are  killed 
by  the  severity  of  the  winter  and  elsewhere  it  seems  probable  that  there 
is  a  regular  upward  migration  in  spring  and  early  summer  from  the 
roots,  the  aerial  colonies  appearing  first  near  the  crown  and  at  a  later 
period  on  the  higher  parts  of  the  trees.  At  any  time  during  the  sum- 
mer and  fall  there  ma}'  be  migrations  to  the  roots,  and  throughout  the 
year  the  subterranean  colonies  are  maintained. 

The  spread  of  the  insect  is  accomplished  in  part  by  the  viviparous 
females,  which  appear  in  late  summer,  but  quite  as  commonly  perhaps 
by  the  transporting  of  young  or  parti}7  grown  individuals  from  tree  to 
tree  or  to  distant  orchards  by  means  of  birds  or  insects  to  which  they 
have  attached  themselves.  Its  wide  distribution  is  usually  dependent 
on  the  traffic  in  nursery  stock. 

REMEDIES   AND    PREVENTIVES. 

The  foregoing  account  of  the  habits  and  characteristics  of  the  woolly 
aphis  will  enable  us  to  suggest  certain  measures  to  control  it.  The 
aerial  form  presents  no  especial  difficulty,  and  can  be  very  readily  exter- 
minated by  the  use  of  any  of  the  washes  recommended  for  aphides, 
such  as  kerosene  emulsion,  a  strong  soap  wash,  resin  wash,  etc.,  the 
only  care  necessary  being  to  see  that  the  wash  is  put  on  with  sufficient 
force  and  thoroughness  to  penetrate  the  covering  and  protecting  cot- 
tony excretion.  If  the  wash  be  applied  warm,  its  penetration  will  be 
considerably  increased. 

The  much  more  important  root  form,  however,  is  more  difficult  to 
reach  and  exterminate.  Any  of  the  remedies  which  are  applicable  to 
the  phylloxera  will  apply  to  the  apple  root-aphis,  such  as  the  use  of 
bisulphid  of  carbon  or  submersion.  The  common  recommendations 
are  of  applications  of  strong  soap  or  tobacco  washes  or  kerosene  emul- 
sion to  the  soil  about  the  crown,  or  soot,  ashes,  or  tobacco  dust  buried 
about  the  roots,  also  similarly  employed  are  lime  and  gas  lime. 

The  most  generally  recommended  measure  hitherto  is  the  use  of  hot 
water,  and  this,  while  being  both  simple  and  inexpensive,  is  thoroughly 
effective,  as  has  been  demonstrated  by  practical  experience.  Water  at 
nearly  the  boiling  point  may  be  applied  about  the  base  of  young  trees 


without  the  slightest  danger  of  injury  to  the  trees,  and  should  be 
in  sufficient  quantity  to  thoroughly  wet   the  Boil  to  .1  depth  ol  Beveral 
inches,  as  tin-  ;i  1  >  1 1  i <  1 1 ■  -  maj  penetrate  nearly  a  foot  below  the  Burl 
To  facilitate  the   wetting  of  the  roots  and   the  extermination  <»f  the 
aphides,  as  much  of  the  Burface  Boil  as  possible  Bhould  be  first  removed. 

Kerosene  emulsion,  at  '_'n  to  30  per  cent  of  kerosene,  has  given  good 
results  in  Georgia,  as  reported  bj  R.  I.  Smith.1 

Mr.  .1.  M.  Stedman  was  the  first  to  demonstrate  the  protective  as  well 
as  remedial  value  of  finely  ground  tobacco  dust.  The  desirability  ol 
excluding  the  aphis  altogether  from  nurserj  stock  i.-  at  once  apparent, 
ami  this  Mr.  Stedman  has  Bhown  to  be  possible  by  placing  tobacco 
du.-t  freely  in  the  trenches  in  which  the  seedlings  or  grafts  are  planted 
and  in  the  orchard  excavations  for  young  trees.  Nursery  Btock  may  be 
continuously  protected  by  laying  each  Bpring  a  line  of  the  dust  in  a 
small  furrow  on  either  side  of  the  row  and  as  close  as  possible  to  the 
tree,  covering  loosely  with  earth.  For  large  tree-,  both  for  protection 
and  the  destruction  of  existing  aphides,  from  2  to  5  pounds  of  the  duel 
should  be  distributed  from  the  crown  outward  to  a  distance  of  2  feet, 
tirst  removing  the  surface  Boil  to  a  depth  of  from  1  to  6  inches. 

Since  it-  early  recommendation  marked  Buccese  has  been  reported 
from  the  use  of  tobacco  dust.  A  notable  instance  is  thai  given  by  Mr. 
M.  B.  Waite,  of  the  Bureau  of  Plant  Industry,  who  applied  a  ton  of 
tobacco  waste,  costing  $25,  in  bis  orchard,  with  the  result  of  entirely 
renewing  the  vigor  of  his  trees  and  producing  a  strong  stubby  growth  of 
twigs.  A  peck  of  tobacco  dust  was  placed  about  each  of  his  larger 
trees  in  a  circle  of  '_'  or  3  feel  around  the  trunk,  and  a  Blightly  smaller 
amount  aboul  trees  from  one  to  three  years  old. 

The  tobacco  kills  the  aphides  By  leaching  through  the  soil,  and  act- 
as  a  bar  for  a  year  or  bo  to  reinfestation.     The  dual  i-  a  waste  producl 
of  tobacco  factories  and  costs  about   1   cent  per  pound,  and  p — 
the  additional  value  of  being  worth  fully  it>  cost  as  a  fertilizer. 

The  use  of  bisulphid  of  carbon  for  the  woolly  aphis  i>  the  aam< 
for  the  grape  root-aphis.  It  Bhould  he  applied  in  two  or  three  holes 
about  the  tree  to  a  depth  of  ii  to  12  inches  and  not  closer  than  H  feel 
to  the  crown.  An  ounce  of  the  chemical  should  he  introduced  into  each 
hole,  which  Bhould  he  immediately  closed.  The  hisulphid  evaporate- 
and  penetrate-  throughout  the  -oil  and  readily  and  promptly  kills  the 
aphides.  It  does  not.  however,  furnish  any  protection  from  future 
attacks,  and  is  attended  witli  danger  to  the  tree  unless  the  precautions 
named  are  carefully  observed.  That  it  is  highly  inflammable  should  also 
instantly  borne  in  mind.  If  it  i^  to  he  used  at  all  extensively,  an 
automatic  injecting  device  should  he  secured.  The  chemical 
about  li>  cents  per  pound  in  50-pound  cat  - 


'Bui.  60,  Bur.  Ent.,  U.  S.  Dept.  1906. 


6 

Badly  infested  nursery  stock  should  be  destroyed,  since  it  would  be 
worth  little  even  with  the  aphides  re  moved.  Slightly  infested  stock  can 
be  easily  freed  of  the  aphides  at  the  time  of  its  removal  from  the  nursery 
rows.  The  soil  should  be  dislodged  and  the  roots  pruned,  and  in 
batches  of  a  dozen  or  so  the  roots  and  lower  portion  of  the  trunk  should 
be  immersed  for  a  few  seconds  in  water  kept  at  a  temperature  of  130° 
to  150  F.  A  strong  soap  solution  similarly  heated  or  a  fifteen  times 
diluted  kerosene  emulsion  will  give  somewhat  greater  penetration  and 
be  more  effective,  although  the  water  alone  at  the  temperature  named 
should  destroy  the  insects.  This  treatment  is  so  simple  and  inexpensive 
that  it  should  always  he  insisted  upon  by  the  purchaser  if  there  be  any 
indication  of  the  presence  of  this  insect,  and  stock  exhibiting  much 
damage  should  be  refused  altogether. 

After  planting,  if  the  trees  be  kept  in  vigorous  growing  condition  by 
careful  cultivation  and,  if  necessary,  proper  fertilizing,  damage  from  the 
aphides  is  much  less  apt  to  occur,  and  the  principal  danger  period, 
namely,  the  first  two  or  three  years  after  planting  in  the  orchard,  will 
pass  in  safetj'.  The  value,  as  a  means  of  protection,  of  thorough  culti- 
vation and  good  care  of  young  orchards  can  not  be  too  strongly 
insisted  upon.  Vigorous  growing  trees  have  a*  decided  power  of  resist- 
ance and  are  able  to  sustain  with  comparatively  little  damage  the 
presence  of  the  root-aphides,  while  illy-cultivated  and  neglected  orchards 
are  especially  liable  to  injury. 

The  woolly  aphis  is  subject  to  the  attacks  of  a  number  of  natural 
enemies,  including  the  parasitic  chalcis  Hy,  Aphelinus  matt  Haldemann, 
and  the  larva  of  a  syrphus  Hy,  Pipiza  radicum  Walsh  and  Riley,  and 
also  the  larva  and  adult  of  several  species  of  ladybirds,  the  larvae  of 
lace-wing  flies,  and  spiders,  etc.  In  the  East  a  very  small  brown  species 
of  ladybird,  Scymnus  eervicalis  Muls.,  is  often  present  in  some  numbers, 
and  the  common  nine-spotted  ladybird,  Cocdnella  9-notata  Hbst.,  is  also 
an  active  enemy  of  the  woolly  aphis.  The  nine-spotted  ladybird  has  been 
used  very  successfully  in  California,  on  the  authority  of  Mr.  Ellwood 
Cooper,  to  rid  trees  of  root-aphides,  this  being  effected  by  colonizing  the 
larvae  of  the  ladybird  at  the  base  of  the  infested  tree.  All  the  para- 
sites mentioned  do  much  to  keep  the  root-aphides  in  check,  and  in  the 
case  of  old  well-established  trees  are  in  most  instances  a  sufficient  pro- 
tection, hut  in  the  case  of  young  trees  and  nursery  stock,  where  the 
damage  from  the  aphis  is  much  more  rapid  and  serious,  the  use  of  the 
direct  remedies  outlined  should  not  be  neglected,  and  particularly  should 
the  nursery  treatment  be  insisted  upon. 

Approved  : 
James  Wilson, 

Secretary  of  Agriculture. 

Washington,  D.  C,  June  23,  1008. 

O 


■in in  in 

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